Many applications exist where a plurality of emitters of electromagnetic energy need to be detected and monitored from a single remote location. For example, a military satellite may be used to sense terrestrial-based enemy radar systems in a predetermined region. In such an application, the remote sensor generally receives a number of electromagnetic pulses generated by the plurality of emitters. The electromagnetic pulses are then sorted and analyzed to derive information about the emitters. Some of the emitters sensed by the sensor may be of high interest to the system operator while others are of relatively low interest.
In the past, pulses were sorted (i.e., deinterleaved) based on measured transmission characteristics of the pulses. That is, each received pulse was analyzed to determine one or more transmission characteristics of the pulse (e.g., frequency, pulse-width, pulse repetition interval, modulation type, etc.) and the resulting information was used to associate the pulse with a particular emitter. The deinterleaved information was then analyzed further to determine more specific information about the identified emitters. Modern emitters (particularly modern radar transmitters), however, are increasingly utilizing pulse agility techniques to avoid detection, jamming, and countermeasure activities. Pulse agility generally refers to the process of changing one or more transmission characteristics from pulse to pulse or from pulse group to pulse group. As can be appreciated, pulses received from a plurality of pulse agile emitters are considerably more difficult, if not impossible, to deinterleave using these past techniques.
To exacerbate the problem, many sensor platforms (e.g., satellite-based sensors) include limited on-board processing capability and must therefore transfer collected data to a remote processing facility to deinterleave and process the received pulse information. For example, satellite-based sensors generally transfer collected emitter information to a ground based processing station to perform the required processing. The links used to carry the collected data to the processing facility (e.g., a satellite downlink) are generally limited in bandwidth and are thus not capable of handling the increased amount of data generated while sensing pulse agile emitters.
Therefore, there is a need for a method and apparatus that is capable of efficiently and practically sensing a plurality of emitters that can include one or more pulse agile emitters. The method and apparatus will preferably be commensurate with the limited processing power and/or data link capacity associated with some current sensor platforms.